This invention relates to a seat belt apparatus installed in a vehicle such as an automobile for protecting a passenger. More particularly, the invention relates to a seat belt retractor in which a reel shaft, which takes up the seat belt, is locked against rotation by movement of the reel shaft in the event of an emergency to prevent the seat belt from being pulled off the reel shaft.
In order to prevent a seat belt from being pulled off a reel shaft by inertial motion of a passenger in the event of an emergency, such as when a large deceleration acts upon the vehicle, the conventional seat belt retractor installed in a vehicle such as an automobile is provided with locking means for locking the reel shaft, which takes up the seat belt, against rotation.
One example of such reel-shaft locking means is as disclosed in the specification and drawings of U.S. Pat. No. 4,796,918. Specifically, frame locking-type locking means is disclosed in which teeth are formed on a reel shaft and on a frame supporting the reel shaft. When deceleration greater than a predetermined value acts upon the vehicle, the reel shaft moves so that its teeth mesh with the teeth on the frame, thereby locking the reel shaft against rotation. This frame locking-type locking means can be formed so as to be comparatively light in weight because the teeth are formed on the frame; therefore, a special member having such teeth is unnecessary. Accordingly, such locking means is fully capable of lending itself to a reduction in weight presently demanded in vehicles such as automobiles.
It is desired that a retractor equipped with such frame locking-type locking means be provided with a comfort device of the kind disclosed in the specification of Japanese Patent Application Laid-Open (KOKAI) No. 1-141147, by way of example. However, since the conventional locking means of the frame locking type is so adapted as to move in a direction parallel to the reel shaft, it is difficult to mount the comfort device in the conventional retractor. Similarly, with the conventional retractor, it is difficult to mount other accessory devices besides the comfort device.